The present invention relates to systems for transporting materials, parts, or any other objects between controlled environments without introducing contamination from an intervening uncontrolled environment, and more particularly to such systems as applied to processes for manufacturing high density electronic integrated circuits and other products requiring similarly clean and carefully controlled environments.
A problem in integrated circuit manufacturing is the presence of particulates and other forms of contamination on and about the wafers on which the circuits are formed. For example, exposure to ambient air gives rise to wafer surface modification, such as by oxidation, nitrification, absorption of water vapors or other impurities, that require additional steps of wafer surface preparation prior to meaningful processing in the receiving apparatus. One of the major sources of particulate contamination is human-generated, including both particles which are released by human bodies and particles which are stirred up by equipment operators moving around inside a semiconductor processing facility. This aspect of the problem has led to the development of various forms of mechanized and automated processing systems, and enclosed carriers for transporting the wafers between and within such systems. However, the mechanisms themselves are potential generators of particulates. Thus the exclusion of particulates continues to be a limiting factor as device dimensions become smaller and smaller because of the need to avoid the presence of smaller and smaller particles, and because of increased demand for larger integrated circuit patterns.
Wafer processing systems and wafer transport carriers are disclosed in U.S. Pat. Nos. 4,995,430 to Bonara et al. and 5,044,871 to Davis et al. These and other prior art systems for preventing contamination of sensitive articles by particulates and the like at and between process stations remain subject to one or more of the following disadvantages:
1. They are ineffective in that they produce particulates that can contaminate the articles, such as by sliding contact between the articles and loosely fitting holders of the articles or spring compression elements that are used for clamping the articles to the holders. Harmful particulates are also produced by sliding contact of operating door hinges ant other mechanisms that are exposed within the environment of the articles. PA1 2. They are unreliable and expensive to produce in that they require sealed contact between a process station element and a mobile, interchangeable carrier of the articles. PA1 3. They are awkward to use in that mechanisms for transporting the articles must retract sufficiently to clear a swinging carrier door. PA1 4. In systems having vertically oriented carrier doors that sealingly close a carrier opening that extends above the articles, particles proximate the carrier opening are subject to being dislodged as the carrier is opened, the particles falling onto the articles. PA1 4. They have limited application in that they cannot be adapted to existing equipment. PA1 (a) providing a carrier for an array of articles, the carrier having first and second carrier portions for defining the first chamber, the articles being supported by the second carrier portion; PA1 (b) enclosing the carrier within the second chamber; PA1 (c) supporting the first carrier portion within the second chamber without producing sliding contact within each of the first and second chambers; and, PA1 (d) opening the carrier by moving the second carrier portion away from the first carrier portion and out of contact therewith without producing sliding contact within the second chamber, PA1 whereby the articles are accessible within the second chamber.
Thus there is a need for a system that permits transport of wafers by a carrier between controlled environments, and that does not exhibit these disadvantages.